1. Field of the Invention
The present invention relates to an LED illuminator suitable for use as a substitute for an illuminator which utilizes a fluorescent lamp. The present invention further relates to an LED lamp which is usable as a substitute for a fluorescent lamp.
2. Description of the Related Art
Conventionally, illumination apparatuses utilizing a fluorescent lamp have been in wide use. Meanwhile, as disclosed in e.g. JP-UM-A-6-54289, illuminators which utilize a light emitting diode (LED) instead of a fluorescent lamp have been developed. An LED has the advantage over a fluorescent lamp in terms of the smaller power consumption and longer life.
FIG. 5 is a wiring diagram showing the conventional LED illuminator disclosed in the above-described gazette. The LED illuminator X illustrated in the figure can be used as mounted to a conventional fluorescent lamp illumination apparatus. In the LED illuminator X, electric power supplied from a commercial 100V AC power supply is reduced by a transformer 91 and then converted into a DC voltage by a rectifier 92 and a capacitor 93. The DC voltage is then applied to a plurality of LEDs 95 via a resistor 94, whereby each of the LEDs 95 is turned on.
Generally, fluorescent lamp illumination apparatuses are designed to input AC current to a fluorescent lamp and generate a high voltage to start discharge. The fluorescent lamp illumination apparatuses include a stabilizer for stabilizing the current to be inputted to a fluorescent lamp after the discharge is started. Fluorescent lamp illumination apparatuses are classified into a starter type, a rapid start type, an inverter type and so on according to the method for lighting a fluorescent lamp. Even if the illumination apparatuses have the same rated voltage, the voltage, current and frequency outputted from the stabilizer vary depending on the lighting method. Moreover, even if the same lighting method is employed, the characteristics of the stabilizer can vary depending on the kind of the fluorescent lamp illumination apparatus.
Thus, to use the LED illuminator X in a conventional fluorescent lamp illumination apparatus, it is necessary to take into consideration the power consumption or the like and adjust the number of series connections and parallel connections of the plurality of LEDs 95 in accordance with the lighting method. Moreover, in the LED illuminator X, the current flowing to each LED 95 tends to vary, resulting in unstable light emission.